1. Field of the Invention
This invention relates to a machine tool including an unclamping lever which is rocked so that a tool attached to a spindle is released from a clamped state.
2. Description of the Related Art
Japanese Laid-open Patent Publication No. 3-92239 (1991) discloses a machine tool of the above-described type. In the disclosed construction, the machine tool comprises a spindle head in which a spindle is provided. A cam is also provided in the spindle head and constitutes unclamping lever pressing means. An unclamping lever is rockably mounted between the spindle and the cam. In exchanging a tool attached to the spindle to another, one end of the unclamping lever is pressed by the cam so that the unclamping lever is rocked. The other end of the unclamping lever then presses a releasing section of the spindle axially with respect to the spindle. With this pressing operation, the tool attached to the spindle is released from a clamped state, and the tool is pushed out. Simultaneously, an exchanging arm of a tool exchanger holds the tool pulling it out of the spindle.
In the above-described machine tool, an amount of press unclamping lever applies to the releasing section of the spindle is sometimes improper due to dimensional errors and wear of parts. When the amount of press by the unclamping lever is smaller, the tool cannot be released from the clamped state. When the amount of press is larger, the tool is released from the clamped state too early. Thus, the tools cannot sometimes be changed efficiently when the amount of press is improper.
In the above-described machine tool, the unclamping lever is rockably mounted on support shafts which are fixed in position. As a result, the amount of press by the unclamping lever cannot be adjusted readily. An adjusting spacer has been proposed to be mounted between the unclamping lever and the releasing section of the spindle. In this case, however, a portion of the machine tool around the unclamping lever and the releasing section needs to be disassembled when the spacer is attached to or detached from the machine tool. The disassembling work and adjustment take much time.